V4L/DVB (5643): Usbvision: make common video and radio ioctls

Radio and video ioctls are the same,
delete the usbvision_do_radio_ioctl function
add the special cases for radio in usbvision_v4l2_do_ioctl

Signed-off-by: Thierry MERLE <thierry.merle@free.fr>
Signed-off-by: Mauro Carvalho Chehab <mchehab@infradead.org>